The scale on which you care about a perceived slight or apparent crisis.
In the face of a hysterical friend or family member, inviting them to check your bothered-o-meter is a polite way of assuring them that you're not fazed.
Friend: "So apparently <insert name of a mutual friends partner that you only invited out of politeness> isn't coming to your party. She's telling people that she's ill, but really she just can't be bothered!"
You: "Really? Check my bothered-o-meter.... nope not even registering."